Reverse link pilot integrated with block codes

ABSTRACT

A technique for encoding digital communication signals. Data symbols are augmented in pilot symbols inserted at predetermined positions. The pilot augmented sequence is then fed to a deterministic error correction block encoder, such as a turbo product coder, to output a coded sequence. The symbols in the error correction encoded sequence are then rearranged to ensure that the output symbols derived from input pilot symbols are located at regular, predetermined positions. As a result, channel encoding schemes can more easily be used which benefits from power of two length block sizes.

RELATED APPLICATION(S)

[0001] This application is a continuation of U.S. application Ser. No.09/728,575, filed Nov. 30, 2000, the entire teachings of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to communications systems and inparticular to a scheme for digital encoding of signals in a wirelesssystem.

[0003] Demand for wireless communications equipment and servicescontinues to grow at an unprecedented rates throughout the world.Increasingly, such systems are commonly relied upon to provide voice anddata communications to a growing sector of the public. While thesesystems originally depended upon analog signaling technology, there isessentially unanimous agreement that future systems will be based onvarious types of digital signal coding schemes.

[0004] The typical wireless communication system is a point tomulti-point type system in which a central base station communicateswith a number of remote units located within a local geographic area ofcoverage known as a cell. This system provides for duplex communicationsuch that signals may be sent in both a forward direction (from the basestation to the remote unit) as well as in a reverse direction (from themobile remote unit back to the base station). In order to supportcommunication between the remote unit and networks such as the PublicSwitched Telephone Network (PSTN), or data networks such as theInternet, the wireless system must also provide for various logicalcomponents and functional entities.

[0005] Consider the Code Division Multiple Access (CDMA) and TimeDivision Multiple Access (TDMA) digital systems presently in widespreaduse. Each of these systems provide for certain logical types of theradio channels that make up the forward link and reverse link. Inparticular, the forward link channels often include a pilot channel,paging channels, and multiple forward traffic channels. The trafficchannels are used to carry the payload data between the base station andthe mobile unit. A pilot channel is also typically required to allow theremote unit to maintain synchronization with the base station. Thepaging channels provide a mechanism for the base station to inform theremote unit of control information, such as the assignment of forwardtraffic channels to particular connections and/or subscriber units.

[0006] Likewise, an access channel is provided in the reverse directionin addition to reverse traffic channels. The access channels allow theremote units to communicate control information with the base station,such as to send messages indicating the need to allocate or deallocateconnections as required.

[0007] Various environmental conditions will affect the performance ofany wireless communications system. These elements include atmosphericsignal path loss, which may often introduce fading and interference.Fading may include variations that are introduced as a result of thespecific terrain within the cell, as well as other types of fading, suchas multi-path fading, that occurs due to signal reflections fromspecific features, such as buildings that cause fluctuations in receivesignal strength. Systems in which the remote unit may be a mobile unit,especially those potentially operating at higher speeds, such as thecellular telephones used in automobiles, are particularly susceptible tomulti-path fading. In such an environment, the signal pathways arecontinually changing at a rapid rate.

[0008] Certain techniques can be used to attempt to eliminate thedetrimental effects of signal fading. One common scheme is to employspecial modulation and/or coding techniques to improve the performancein a fading environment. Coding schemes such as block or convolutionalcoding add additional parity bits at the transmitter. These codingschemes thus provide increased performance in noisy and/or fadingenvironments at the expense of requiring greater bandwidth to send agiven amount of information.

[0009] In addition, pilot signals may also be used to provide areference for use in signal demodulation. For example, most digitalwireless communications systems provide for a dedicated pilot channel onthe forward link. This permits the remote units to remain in timesynchronization with the base station. Certain systems, such as theIS-95 CDMA system specification promulgated by the TelecommunicationsIndustry Association (TIA) uses the pilot signals that includepseudorandom binary sequences. The pilot signals from each base stationin such a system typically use the identical pseudorandom binarysequence, with a unique time offset being assigned to each base station.The offsets provide the ability for the remote stations to identify aparticular base station by determining this phase offset in the forwardlink pilot channel. This in turn permits the remote units to synchronizewith their nearest neighboring base station. Coding the pilot channel inthis way also helps support other features, such as soft handoff forcell-to-cell mobility.

[0010] The pilot signal, having a predictable frequency and rate, allowsthe remote units to determine the radio channel transfercharacteristics. By making such determinations, the receiver may in turnfurther compensate for the distortion introduced in the channel duringthe process of estimating symbols being received.

[0011] However, it is generally considered to be impractical to usepilot signals in the reverse link. In particular, this would lead to asituation where pilot signal channels would have to be dedicated foreach remote unit. While this would not necessarily pose a problem in apoint to point system, in point to multi-point systems such as acellular telephone network, the architecture would quickly lead toinefficiency in use of the available radio spectrum. In addition, it isgenerally thought that the overhead associated with a system thatassigned individual pilot channels to each remote unit wouldunnecessarily complicate the base station receiver processing.

[0012] An alternative to allocating individual pilot channels is to makeuse of a sequence of pilot symbols. The pilot symbols are interleavedwith data symbols on the traffic channel. This technique is generallyreferred to as pilot symbol assisted modulation. In such a system, thetransmitter encodes the data to be sent on the traffic channel as aseries of symbols. A pilot symbol interleaver then inserts a sequence ofpredetermined pilot symbols within the data symbol sequence. The pilotsymbol augmented sequence is then modulated and transmitted over theradio channel. At the receiving station, a decimater or deinterleaverand filter separate the pilot symbols from the data symbols.

SUMMARY OF THE INVENTION

[0013] What is needed is a way to integrate pilot symbol assistedmodulation techniques with block encoding schemes in a way in whichmaximizes the probability that data and pilot symbols will be correctlyreceived.

[0014] The invention accomplishes this with a pilot symbol insertionscheme that proceeds as follows. The source data bits are firstaugmented with periodically inserted pilot symbols. In a preferredembodiment, the pilot symbols are inserted at a position correspondingto a power of two, such as for example, every fourth, eighth, sixteenth,or thirty-second symbol. Next, this pilot symbol augmented data sequenceis presented to a deterministic block coder. Such a block coder may, forexample, be a sub-rate two dimensional turbo product coder.

[0015] The symbols of the resulting encoded block are then rearrangedsuch that the pilot symbols will be in a predictable location. Becausethe pilot symbols are always in a known place in the input block codingmatrix, their positions are therefore also known in the output blockcoding matrix. The encoded output pilot symbols can therefore berearranged such that they are evenly distributed through the outputcoded space, prior to modulation and transmission.

[0016] An optional embodiment makes use of an interleaving scheme inwhich parity symbols are interleaved with data and pilot symbols. Insuch a scheme, all symbols from the coded space, with the exception ofthe pilot symbols, are placed in a temporary storage area by row. Datais then read out of the temporary storage area to provide theinterleaved output, by reading data from the temporary array in columnorder. For example, a first pilot signal is selected, a row is read out,a second pilot signal is selected, a second row is read out, and so on.As a result, the pilot symbols are output at predetermined positionspreferably located within symbol positions which are a power of two awayfrom each other.

[0017] In an alternate embodiment, the symbols may be composed of pairsof input data bits, to form complex-valved symbols, which can then bemodulated using Quadrature Phase Shift Keyed (QPSK) schemes. In thisembodiment, the data, parity, and pilot bits are processed in pairs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a block diagram of a communication system which encodespilot symbols according to the invention;

[0019]FIG. 2 is a more detailed diagram of a transmit encoder andreceive decoder;

[0020]FIGS. 3A and 3B illustrate how a deterministic block encoder, suchas a one-quarter rate turbo product encoder, distributes data and paritybits in an output matrix;

[0021]FIGS. 3C and 3D illustrate how the pilot inserter and blockencoder operate according to the invention;

[0022]FIG. 4A illustrates how a first type of interleaver outputs pilot,data, and parity bits;

[0023]FIGS. 4B and 4C illustrate how a second type of interleaver mayorder the data, parity, and pilot bits; and

[0024]FIG. 4D illustrates how a third type of interleaver may orderdata, parity and pilot bits for use with a Quadrature Phase Shift Keyed(QPSK) type modulator.

[0025] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026]FIG. 1 is a block diagram of a communication system 10 thatinterleaves pilot symbols with data symbols and uses a systematic blockcoder to ensure that the pilot symbols are located in predeterminedlocations. In the following description of a preferred embodiment, thecommunication system 10 is described such that the shared channelresource is a wireless or radio channel. However, it should beunderstood that the techniques described here may be applied to allowshared access to other types of media such as telephone connections,computer network connections, cable connections, and other physicalmedia to which access is granted on a demand driven basis.

[0027] The communication system 10 includes a number of PersonalComputer (PC) devices 12-1, 12-2, . . . 12-h, . . . 12-l, correspondingSubscriber Access Units (SAUs) 14-1, 14-2, . . . 14-h, . . . 14-l, andassociated antennas 16-1, 16-2, . . . 16-h, . . . 16-l. Centrallylocated equipment includes a base station antenna 18, and a Base StationProcessor (BSP) 20. The BSP 20 provides connections to an from anInternet gateway 22, which in turn provides access to a data networksuch as the Internet 24, and network file server 30 connected to thenetwork 22. The system 10 is a demand access, point to multi-pointwireless communication system such that the PCs 12 may transmit data toand receive data from network server 30 through bi-directional wirelessconnections implemented over forward links 40 and reverse links 50. Itshould be understood that in a point to multi-point multiple accesswireless communication system 10 as shown, a given base stationprocessor 20 typically supports communication with a number of differentsubscriber access units 14 in a manner which is similar to a cellulartelephone communication network.

[0028] The PCs 12 may typically be laptop computers 12-1, handheld units12-h, Internet-enabled cellular telephones or Personal Digital Assistant(PDA)-type computers. The PCs 12 are each connected to a respective SAU14 through a suitable wired connection such as an Ethernet-typeconnection.

[0029] An SAU 14 permits its associated PC 12 to be connected to thenetwork file server 30 through the BSP 20, gateway 22 and network 24. Inthe reverse link direction, that is, for data traffic traveling from thePC 12 towards the server 30, the PC 12 provides an Internet Protocol(IP) level packet to the SAU 14. The SAU 14 then encapsulates the wiredframing (i.e., Ethernet framing) with appropriate wireless connectionframing. The appropriately formatted wireless data packet then travelsover one of the radio channels that comprise the reverse link 50 throughthe antennas 16 and 18. At the central base station location, the BSP 20then extracts the radio link framing, reformatting the packet in IP formand forwards it through the Internet gateway 22. The packet is thenrouted through any number and/or any type of TCP/IP networks, such asthe Internet 24, to its ultimate destination, such as the network fileserver 30.

[0030] Data may also be transmitted from the network file server 30 tothe PCs 12 in a forward direction. In this instance, an InternetProtocol (IP) packet originating at the file server 30 travels throughthe Internet 24 through the Internet gateway 22 arriving at the BSP 20.Appropriate wireless protocol framing is then added to the IP packet.The packet then travels through the antenna 18 and 16 to the intendedreceiver SAU 14. The receiving SAU 14 decodes the wireless packetformatting, and forwards the packet to the intended PC 12 which performsthe IP layer processing.

[0031] A given PC 12 and the file server 30 can therefore be viewed asthe end points of a duplex connection at the IP level. Once a connectionis established, a user at the PC 12 may therefore transmit data to andreceive data from the file server 30.

[0032] The reverse link 50 actually consists of a number of differenttypes of logical and/or physical radio channels including an accesschannel 51, multiple traffic channels 52-1, . . . 52-t, and amaintenance channel 53. The reverse link access channel 51 is used bythe SAUs 40 to send messages to the BSP 20 to request that trafficchannels be granted to them. The assigned traffic channels 52 then carrypayload data from the SAU 14 to the BSP 20. It should be understood thata given IP layer connection may actually have more than one trafficchannel 52 assigned to it. In addition, a maintenance channel 53 maycarry information such as synchronization and power control messages tofurther support transmission of information over the reverse link 50.

[0033] Similarly, the forward link 40 typically includes a pagingchannel 41. The paging channel 41 is used by the BSP 20 to not onlyinform the SAU 14 that forward link traffic channels 52 have beenallocated to it, but also to inform the SAU 14 of allocated trafficchannels 52 in the reverse link direction. Traffic channels 42-1 . . .42-t on the forward link 40 are then used to carry payload informationfrom the BSP 20 to the SAUs 14. Additionally, maintenance channels carrysynchronization and power control information on the forward link 40from the base station processor 20 to the SAUs 14.

[0034] In the preferred embodiment, the logical channels 41-43 and 51-53are defined by assigning each channel a unique pseudorandom channel (PN)code. The system 10 is therefore a so-called Code Division MultipleAccess (CDMA) system in which channels assigned to unique codes may usethe same radio carrier frequency. The channel may also be furtherdivided or assigned. Additional information as to one possible way toimplement the various channels 41, 42, 43, 51, 52, and 53 is provided inPatent Cooperation Treaty Application No. WO99/63682 entitled “FastAcquisition Of Traffic Channels For A Highly Variable Data Rate,”assigned to Tantivy Communications, Inc., and published Dec. 9, 1999. Ina preferred embodiment, the channel codes are a type of PN code whichrepeats at a code length of ₂N. One such orthogonal PN code scheme isdescribed in U.S. patent application Ser. No. 09/255,156, filed Feb. 23,1999, entitled “Method and Apparatus for Creating Non-InterferingSignals Using Non-Orthogonal Techniques”, assigned to TantivyCommunications, Inc.

[0035] Turning attention now to FIG. 2 there is shown a generalizedblock diagram of the encoding process at the transmit side and decodingprocess at the receive side according to the invention. It should beunderstood that the invention is implemented on the reverse link 50, sothat the transmitter 100 may typically be one of the SAUs 14 and thereceiver is the Base Station Processor (BSP) 20. However, in otherimplementations it is possible for the invention to be applied on theforward link 40, in which case the transmitter is implemented in the BSP20 and the receivers is the SAUs 14.

[0036] In any event, a transmitter 100 is implemented with a pilotinserter 110, block encoder 120, pilot interleaver 130, channel coder140 and radio frequency (RF) modulator 150. The receiver 200 includes anRF demodulator 250, channel decoder 240, pilot deinterleaver 230, blockdecoder 220, pilot removal 210, and pilot reference generator 205.

[0037] It should be understood that the receiver 200 performs theinverse functions of the corresponding portions of the transmitter 100.In such an instance, the RF demodulator 250 performs the inverse radiofrequency to modulation process, the channel decoder 240 decodes thechannel codes reversing the operation of the channel coder 140, thepilot deinterleaver 230 performs the inverse function of the specificpilot interleaver 130 implemented in the transmitter, and the blockdecode process 220 also undoes the block encode process 120. The pilotremoval process 210 uses a pilot reference signal generator 205, forexample, to multiply the received data in pilot stream via referencepilot signal to further aid in the recovery of the data. A pilotinserter 110 typically makes sense in the reverse link 50 given and thatpilot symbols are preferably inserted with the data symbols or bits inthis same channel. This is opposed to an arrangement where there areseparate pilot channels devoted separately for simply sending pilotsignals, which is typically more practical on the forward link 40, inwhich case a single pilot channel can be associated with and be sharedby numerous SAUs 14.

[0038] Before discussing the details of the pilot inserter 110 and blockencoder 120 in more detail, it is instructed to consider the operationof a typical error coding process. In particular, consider an examplesituation in the use of a turbo product code which is to encode data atthe rate of ¼. (We assume in the discussion of this first embodimentthat data is real-valued only such that a “symbol” is a single data bit,and discuss a situation with complex-valued data symbols later on.) Inthe case shown in FIG. 3A, the input data bits data₁, data₂ . . . data₁₆may thought of as being placed in the upper left hand corner of a matrixencoding space. Because the code is a ¼ rate code, the matrix encodingspace consists of a matrix which is four times the size of the inputdata matrix space. In the current example the input data matrix space is4×4, and the coded space is a matrix of 8×8.

[0039] For a typical prior art block coding operation, that is onewithout supplementation with pilot symbols according to the invention,the 16 input data bits are placed an upper left hand corner of the 8×8encoded space as shown in FIG. 3A.

[0040] The encoded matrix is then presented to the block encoder tocalculate and create the parity bits for an encoded space. In theexample being discussed, in the case of a ¼ rate code, three times asmany parity bits as data bits are calculated and created as shown inFIG. 3B. This type of systematic turbo product code, is considered to bedeterministic in the sense that input data bits appear in the sameposition in the output matrix as they do in the input matrix, with allof the parity bits taking up the other spaces in the matrix.

[0041] Returning attention to FIG. 2, the pilot inserter 110 and blockencoder 120 can now be understood more particularly. In the pilotinsertion scheme employed by the pilot inserter 110, some of the inputdata symbols are replaced with pilot symbols. In the preferredembodiment, the goal is to have pilot symbols make up approximately6.25% of the data symbols sent on the channel after encoding. That meansfor every 64 channel symbols there needs to be 4 pilot symbols insertedinto the information space.

[0042] Turning attention to FIG. 3C, we see that in considering a groupof 16 data symbols, 4 of the symbols will be replaced with pilot symbolssuch that the input matrix becomes as shown. Thus a pilot symbol,pilot₁, is followed by three data symbols, data₁, data₂, data₃. The nextpilot symbol, pilot₂, is followed by data symbols data₄, data₅, data₆and so on.

[0043] As in the case of the standard turbo product code, the matrix inFIG. 3C is then presented to the block encoder 120 to create the encodedspace shown in FIG. 3D. The parity symbols of this example will, infact, be different from those for the situation where the non-insertedinformation space because the information space has changed between thetwo examples. In particular, of course, the information space in FIG. 3Cis different from the information space in FIG. 3A, and so the paritysymbols parity₁, parity₂ . . . parity48 are different. What is importantto note here is that the pilot symbols pilot1, pilot2, pilot3 and pilot4 are still in the same identifiable positions in the matrix.

[0044] It is the job of the pilot interleaver 130 to rearrange theoutput matrix in such a manner that the pilot symbols are evenlydistributed among the data and parity symbols in a manner which makessense. In the simplest instance, the data and parity symbols can beplaced on the channel in, more or less, the order in which they appearin the matrix. This situation is shown in FIG. 4A. In particular, it isnoted that the pilot symbols pilot₁, pilot₂, pilot₃ are redistributedthrough the matrix so that they are read out once every 16 bits, or6.25% of the time, as desired. The matrix can thus be interpreted as aset of instructions for ordering the output bits, by reading along thefirst row, and then reading the bits out along the second row, and thenalso the third row, and so on.

[0045] In certain other instances it is important to interleave theparity symbols among the pilot and data symbols as well. In thissituation, the parity symbols and data symbols can be better distributedthroughout the information space. In this approach, all except the pilotsymbols may be placed in a temporary storage area 180 in row orderfashion and then read out by column order. The goal in allocating rowsand columns in the temporary storage area 180 is to remain as square aspossible. Thus, in the example illustrated shown in FIG. 4B, the dataand parity symbols are first read out from a first row of the codedoutput matrix in FIG. 4A, while saving the pilot symbols in anothertemporary storage area. The result is a matrix having the data₁, data₂,data₃, parity₁, parity₂, parity₃ . . . parity₄₇, parity₄₈ symbolarrangement as shown. Data is then read out of this temporary storagearea 180 by reading out the non-pilot symbols in column order. Thus, forexample, as shown in FIG. 4C, a first pilot symbol is read out of thepilot matrix, and then fifteen symbols are read from the non-pilotstorage area (data₁, parity₄, parity₇, parity₁₀, and so on) resulting inthe order of symbols shown in the first row of FIG. 4C. This results notonly in the pilot symbols continuing to be distributed once every 16symbols, but also in a situation such that the data symbols are moreevenly disbursed throughout the encoded space.

[0046] In yet another example of the implementation of the interleaver130, it may be advantageous to apply data to the channel with QuadraturePhase Shift Keyed (QPSK) format modulation. In this case, individualinput data bits are read in pairs so that for example, 2 pilot bits arerequired to make up respectively the In-phase (I) and the Quadrature (Q)portion of a complex valued data symbol. In this case, pilot bits arealso read out in pairs so that two pilot bits comprise a pilot symbol.The result, as shown in FIG. 4D, is a situation in which pilot symbols(consisting of a pilot1 and pilot₂ bit) still appear every 16 symbols or6.25% of the time.

[0047] Using the systematic block encoder, the position of the pilot,information, and parity symbols is always known in the output matrix.This creates a structure where pilot symbols can be repositioned in aknown fashion, to ensure that they repeat in a regular pattern in themodulated output signal.

[0048] For example, a system timing requirement may demand that theratio of pilot symbols to the ratio of data and parity symbols remain ata power of two, so that clock phasing requirements are much easier tomeet. In particular, even if a block encoder produces a number of dataand parity symbols as a power of 2, the additional pilot symbolinsertions would create an output sequence which is not an exact powerof 2. This makes it difficult to insert pilot symbols in blocks which donot remain in phase, and therefore “roll” with respect to the PNsequences used with respective channel encoding 140. For example, in acase where pilot symbols need to be inserted 6.25% of the time, a blockof 4096 would require 4096 for data and parity, plus 6% of 4096, or 256symbols for pilots for a total of 4352 symbols per block. Because no PNchannel code is such a length, to maintain synchronization, the positionof the PN code would change at the start of every symbol block. However,with the invention, this difficulty is avoided, and the output symbolblocks are easily contrived to be in groups of ₂N, including both parityand pilot symbols. Thus, PN code synchronization timing, as required tomaintain the proper spread spectrum characteristics, is easy.

What is claimed is:
 1. A method for encoding an input digital bit streamfor communication over a channel, the channel being defined by coding,the method comprising the steps of: selecting a group of input digitalbits as an input symbol block, and forming data symbols therein;inserting pilot symbols in the input symbol block, the pilot symbolbeing inserted into predetermined positions within the input symbolblock; encoding the symbol block with a systematic block coder, thesystematic block coder producing an encoded symbol block which includesdata symbols, pilot symbols, and parity symbols in deterministiclocations; and interleaving the pilot symbols within the encoded symbolblock to produce an output symbol block consisting of data symbols andparity symbols, as well as pilot symbols located at intervals within theoutput symbol block.
 2. A method as in claim 1 additionally comprisingthe steps of: modulating the output symbol block with coding to providea channel signal.
 3. A method as in claim 2 wherein the coding ispseudonoise (PN) sequence coding.
 4. A method as in claim 3 wherein thePN sequence repeats at a length of 2^(N).
 5. A method as in claim 1wherein data symbols in the input block each correspond to a single bitof the input sequence.
 6. A method as in claim 1 wherein data symbols inthe input block are each composed of two bits of the input sequence. 7.A method as in claim 1 wherein the systematic block coder is a turboproduct code.
 8. A method as in claim 1 wherein the steps ofinterleaving the pilot symbols comprises the steps of: storing the dataand parity symbols in the encoded symbol block in a temporary storagematrix in row order; reading out the contents of the temporary storagematrix in column order, and augmenting each such column with a pilotsymbol.
 9. A method for decoding a received symbol stream into an outputdigital bit stream, the symbol stream including at least one outputsymbol block from a transmitter, the output symbol block including datasymbols, pilot symbols, and parity symbols, the method comprising thesteps of: selecting an output symbol block within the received symbolstream; de-interleaving the pilot symbols located at intervals withinthe output symbol block to produce an encoded symbol block that includesdata symbols, pilot symbols, and parity symbols in deterministiclocations; decoding the encoded symbol block using a systematic blockdecoder, the systematic block decoder producing a symbol block whichincludes data symbols and pilot symbols in deterministic locations; andremoving the pilot symbols in the symbol block, the pilot symbols beingremoved from predetermined positions within the symbol block to producea group of output data symbols that forms a group of output digital bitsof the output digital bit stream.
 10. A method as in claim 9additionally comprising the steps of: generating a reference pilotsignal and multiplying the reference pilot signal with the data in thepilot stream.
 11. A method as in claim 9 additionally comprising thesteps of: demodulating a signal received from a communications channeldefined by coding to produce the received symbol stream.
 12. A method asin claim 11 wherein the coding is PN sequence coding.
 13. A method as inclaim 12 wherein the PN sequence repeats at a length of 2^(N).
 14. Amethod as in claim 9 wherein data symbols in the symbol block eachcorrespond to a single bit of the output digital bit stream.
 15. Amethod as in claim 9 wherein data symbols in the symbol block are eachcomposed of two bits of the output digital bit stream.
 16. A method asin claim 9 wherein the systematic block decoder is a turbo product code.17. A method as in claim 9 wherein the steps of de-interleaving thepilot symbols comprises the inverse of the steps of claim
 8. 18. Anapparatus for encoding an input digital bit stream for communicationover a channel, the channel being defined by coding, the input digitalbit stream being grouped into input symbol blocks with data symbolstherein, the apparatus comprising: a pilot inserter unit that insertspilot symbols in the input symbol block, the pilot symbol being insertedinto predetermined positions within the input symbol block; a systematicblock encoder unit that produces an encoded symbol block which includesdata symbols, pilot symbols, and parity symbols in deterministiclocations; and an pilot interleaver unit that interleaves the pilotsymbols within the encoded symbol block to produce an output symbolblock consisting of data symbols and parity symbols, as well as pilotsymbols located at intervals within the output symbol block.
 19. Anapparatus as in claim 18 additionally comprising a channel coder unitthat modulates the output symbol block with coding to provide a channelsignal.
 20. An apparatus as in claim 19 wherein the coding is a PNsequence coding.
 21. An apparatus as in claim 20 wherein the PN sequencerepeats at a length of 2^(N).
 22. An apparatus as in claim 18 whereindata symbols in the input block each correspond to a single bit of theinput sequence.
 23. An apparatus as in claim 18 wherein data symbols inthe input block are each composed of two bits of the input sequence. 24.An apparatus as in claim 18 wherein the systematic block coder is aturbo product code.
 25. An apparatus as in claim 18 wherein the pilotinterleaver unit performs interleaving by storing the data and paritysymbols in the encoded symbol block in a temporary storage matrix in roworder, reading out the contents of the temporary storage matrix incolumn order, and augmenting each such column with a pilot symbol. 26.An apparatus for decoding a received symbol stream into an outputdigital bit stream, the symbol stream including at least one outputsymbol block from a transmitter, the at least one output symbol blockbeing selected for decoding, the output symbol block including datasymbols, pilot symbols, and parity symbols, the apparatus comprising: apilot deinterleaver unit that de-interleaves the pilot symbols locatedat intervals within the output symbol block to produce an encoded symbolblock that includes data symbols, pilot symbols, and parity symbols indeterministic locations; a systematic block decoder unit that decodesthe encoded symbol block, the systematic block decoder producing asymbol block which includes data symbols and pilot symbols indeterministic locations; and a pilot removal unit that removes the pilotsymbols from the symbol block, the pilot symbols being removed frompredetermined positions within the symbol block to produce a group ofoutput data symbols that forms a group of output digital bits of theoutput digital bit stream.
 27. An apparatus as in claim 26 additionallycomprising a pilot reference signal generator unit coupled to the pilotremoval unit that generates a reference pilot signal to enable the pilotremoval unit to multiply the reference pilot signal with the data in thepilot stream.
 28. An apparatus as in claim 26 additionally comprising achannel decoder unit that demodulates a signal received from acommunications channel defined by coding to produce the received symbolstream.
 29. An apparatus as in claim 28 wherein the coding is PNsequence coding.
 30. An apparatus as in claim 29 wherein the PN sequencerepeats at a length of 2^(N).
 31. An apparatus as in claim 26 whereindata symbols in the symbol block each correspond to a single bit of theoutput digital bit stream.
 32. An apparatus as in claim 26 wherein datasymbols in the symbol block are each composed of two bits of the outputdigital bit stream.
 33. An apparatus as in claim 26 wherein thesystematic block decoder is a turbo product code.
 34. An apparatus as inclaim 26 wherein the pilot deinterleaver unit performs the inverse ofthe steps performed by the pilot interleaver unit of claim
 25. 35. Asystem for encoding an input digital bit stream for communication over achannel, the channel being defined by coding, the system comprising:means for selecting a group of input digital bits as an input symbolblock, and forming data symbols therein; means for inserting pilotsymbols in the input symbol block, the pilot symbol being inserted intopredetermined positions within the input symbol block; means forencoding the symbol block with a systematic block coder, the systematicblock coder producing an encoded symbol block which includes datasymbols, pilot symbols, and parity symbols in deterministic locations;and means for interleaving the pilot symbols within the encoded symbolblock to produce an output symbol block consisting of data symbols andparity symbols, as well as pilot symbols located at intervals within theoutput symbol block.
 36. A system as in claim 35 additionallycomprising: means for modulating the output symbol block with coding toprovide a channel signal.
 37. A system for decoding a received symbolstream into an output digital bit stream, the symbol stream including atleast one output symbol block from a transmitter, the output symbolblock including data symbols, pilot symbols, and parity symbols, thesystem comprising: means for selecting an output symbol block within thereceived symbol stream; means for de-interleaving the pilot symbolslocated at intervals within the output symbol block to produce anencoded symbol block that includes data symbols, pilot symbols, andparity symbols in deterministic locations; means for decoding theencoded symbol block using a systematic block decoder, the systematicblock decoder producing a symbol block which includes data symbols andpilot symbols in deterministic locations; and means for removing thepilot symbols in the symbol block, the pilot symbols being removed frompredetermined positions within the symbol block to produce a group ofoutput data symbols that forms a group of output digital bits of theoutput digital bit stream.
 38. A system as in claim 37 additionallycomprising: means for generating a reference pilot signal andmultiplying the reference pilot signal with the data in the pilotstream.
 39. A system as in claim 37 additionally comprising: means fordemodulating a signal received from a communications channel defined bycoding to produce the received symbol stream.